The present application relates to an imaging device including a photoelectric conversion element which photoelectrically converts incident light, and generates and amplifies a signal charge, and relates to an electronic device using the imaging device.
As a solid-state imaging device with high sensitivity, there is an imaging device in which a phototransistor is included as a photoelectric conversion element. Since larger output is obtained with respect to light by an amplifying function which the phototransistor has than by a photodiode, it is possible to achieve higher sensitivity compared to a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) image sensor using the photodiode as the photoelectric conversion element. On the other hand, regarding an optical input range (dynamic range), in an accumulation drive type which is the main stream at present, it is already known that an upper limit is determined by a saturated amount of accumulable charge in junction capacitance as well as other sensors.
For example, in Japanese Patent Application Publication No. 2013-187527, for the purpose of expanding a dynamic range, a solid-state imaging device in which a phototransistor is included as a photoelectric conversion element is disclosed. This invention discloses a method of expanding a dynamic range in which an implanted electrode which is insulated by an oxide film exists between elements, and an amplification factor is varied by applying a voltage to the electrode and a photocurrent is changed.